The invention relates to substituted chromane compounds that are modulators of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein, useful in treating diseases and conditions mediated and modulated by CFTR. Additionally, the invention relates to compositions containing compounds of the invention and processes for their preparation.
Cystic fibrosis (CF), one of the most common autosomal recessive genetic diseases in the Caucasian population, is caused by loss of function mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene, which is located on chromosome 7 (http://www.cff.org/AboutCF/; Rowe S. M et al. (2005); N Eng J Med. (352), 1992-2001). Approximately 1:3500 and 1:3000 infants born in the United States and in Europe, respectively, are affected by CF, resulting in ˜75,000 cases worldwide, ˜30,000 of which are in the United State. Approximately 1,000 new cases of CF are diagnosed each year, with more than 75% of patients being diagnosed by 2 years of age. Nearly half the CF population is currently 18 years of age and older. The CFTR protein (Gregory, R. J. et al. (1990) Nature 347:382-386; Rich, D. P. et al. (1990) Nature 347:358-362; Riordan, J. R. et al. (1989) Science 245:1066-1073) is a cAMP/ATP-mediated ion channel expressed in a variety of cell types, including secretory and absorptive epithelial cells. CFTR regulates chloride and bicarbonate anion flux across the cell membrane, maintaining electro neutrality and osmolarity across the epithelial membrane (Quinton, P. M. (1990), FASEB J. 4: 2709-2727). CFTR is also responsible for regulating the activity of other ion channels and proteins (Guggino, W. B. et al. (2006), Nat Revs Molecular Cell Biology 7, 426-436).
Aberrations in CFTR function result in imbalance of the airway surface liquid, leading to mucus dehydration, inflammation, recurrent bacterial infection and irreversible lung damage, which lead to premature death in affected patients. Besides respiratory disease, CF patients suffer from gastrointestinal problems and pancreatic insufficiency. The majority of males (95%) with cystic fibrosis are infertile as a result of azoospermia caused by altered vas deferens; which may be absent, atrophic, or fibrotic. Fertility is also decreased among females with cystic fibrosis due to abnormal cervical mucus.
The F508del mutation, the most common of the approximately 1900 identified polymorphisms in CFTR, results in defective processing of CFTR in the endoplasmic reticulum (ER) (http://www.cftr2.org/index.php). Approximately 90% of the CF patients carry at least one copy of the F508del mutation (deletion of a phenylalanine on position 508), and 50%-60% of the patients are homozygous for this mutation. The defective processing of CFTR results in early CFTR degradation, which leads to reduced trafficking or absence of the protein on the membrane. As there have been over 100 CF disease-causing mutations identified, they have been classified according to their phenotypic consequences and belong to synthesis, maturation, regulation, conductance, reduced number due to quantity and reduced number due to stability classifications.
Current CF drug discovery efforts focus upon developing two classes of compounds to modulate CFTR. One class, called Correctors, helps to overcome the folding defects of the mutated CFTR protein to promote its maturation resulting in higher cell surface expression. The other classes of compounds, called Potentiators, help overcome the defective regulation and/or conductance of the protein by increasing the probability of channel opening on the membrane surface.
In addition, as the modulation of CFTR protein mutations to promote proper protein folding is beneficial for CF, there are other diseases mediated by CFTR. For example, Sjögren's Syndrome (SS), an autoimmune disorder that results in symptoms of xerostomia (dry mouth) and keratoconjunctivitis sicca (KCS, dry eyes) may result from dysregulation of moisture producing glands throughout the body. Chronic obstructive lung disease (COLD), or chronic obstructive airway disease (COAD), which is a progressive and irreversible airflow limitation in the airways is result of several physiologic abnormalities, including mucus hyper secretion and impaired mucociliary secretion. Increasing the anion secretion by CFTR potentiators have been suggested to overcome these phenotypic complexities with Sjögren's Syndrome by increasing the corneal hydration and by overcoming the impaired mucociliary secretion in COAD (Bhowmik A, et al. (2009) Vol. 103(4), 496-502; Sloane P, et al. PLOS One (2012) Vol 7(6), 239809 (1-13)).
Accordingly, there is a need for novel compounds able to modulate CFTR. In particular, the present invention discloses compounds that may act as CFTR modulators for the treatment of cystic fibrosis. The present invention also provides methods for the preparation of these compounds, pharmaceutical compositions comprising these compounds and methods for the treatment of cystic fibrosis by administering the compounds of the invention.